In an imaging apparatus using a solid-state image sensing device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, an optical filter having various optical functions is arranged, for example, between an imaging lens and the solid-state image sensing device so as to successfully reproduce a color tone and obtain a clear image. Its typical example is a near-infrared cut filter, which blocks light in a near infrared wavelength region so as to correct the spectral sensitivity of the solid-state image sensing device to the visibility of human, and is normally arranged between the imaging lens and the solid-state image sensing device Further, in the imaging apparatus, a blocking member that is a so-called diaphragm is arranged to adjust the amount of light incident thereon to thereby avoid a situation that the image sensing device cannot perform imaging any longer because of saturation of electric charges generated due to light reception, or to cut stray light due to reflection or scattering from an optical member such as a lens or a sensor, or a holding member therefore in the imaging apparatus.
In recent years, the imaging apparatus using the solid-state image sensing device is increasingly downsized and becomes to be installed in a small electronic device such as a cellular phone. Thus, the need for downsizing and higher functionality of the electronic device itself is increased recently, along with which the imaging apparatus is also required to be further downsized.
As a method of realizing the downsizing the imaging apparatus, for example, a method of integrally providing a black coating (light blocking film) functioning as a light blocking member at the optical filter is known. In this method, a space for arranging the diaphragm becomes unnecessary, leading to downsizing of the device. In addition, the number of parts can be reduced and simplification of assembly process can be achieved accordingly.
However, in the optical filter integrally provided with the black coating as described above, a phenomenon that light is diffracted near a boundary between the black coating and an opening portion transmitting the light arises, so that unnecessary light is incident on the image sensing device to degrade the image quality in some cases.
An object of the present invention is to provide an optical filter excellent in productivity and economic efficiency and integrally provided with a light blocking film capable of suppressing stray light causing image degradation.
An optical filter according to an aspect of the present invention is an optical filter used for an imaging apparatus having a built-in image sensing device on which light from a subject or a light source is incident, the optical filter including: an optical filter main body arranged between the subject or the light source and the image sensing device and having a transmission property for the incident light; and a frame-shaped light blocking film integrally formed on at least one surface of the optical filter main body, wherein the frame-shaped light blocking film satisfies the following condition (1) and/or condition (2).
(1) A concavity/convexity is formed on at least a part of an inner peripheral surface of the frame-shaped light blocking film in planar view.
(2) A thin part is formed on at least a part of an inner edge of the frame-shaped light blocking film.
According to the present invention, an optical filter excellent in productivity and economic efficiency and integrally provided with a light blocking film capable of suppressing stray light causing image degradation can be provided.